Wind tunnels are hollow structural facilities in which the aerodynamic qualities and durability of rigid objects such as vehicles or buildings may be evaluated. For example, a prototype of an airplane may be placed within a wind tunnel and subjected to artificially generated flows of air or other gases in order to evaluate the effects of aerodynamic forces or moments on the airplane, such as by simulating flight. Additionally, the air or other gases may be charged with particulate matter or liquids in order to simulate the destructive effects that such materials may have on the airplane when the airplane comes into contact with such gases, particulate matter or liquids during actual flight at various speeds or altitudes, or to provide visible indications of the flows of the air or other gases. Likewise, a model of a dwelling or other building may be constructed or installed within an air tunnel, in order to simulate the effects of adverse weather events on dwellings or buildings of similar sizes or shapes. Air flows within a wind tunnel may be generated by one or more fans or like machines, e.g., devices having one or more rotating bladed impellers, which may be oriented to cast air upon objects being evaluated at desired pressures or velocities.
By their very nature, wind tunnels must be constructed according to strict design requirements and include specialized equipment for performing any operational tests that may be desired. For example, the wind tunnel must include an enclosure around a testing environment that is large enough to accommodate any and all objects or prototypes thereof that may be subjected to such operational tests, from jumbo jets to single-rotor helicopters, or from single-family homes to apartment buildings. For this reason, many wind tunnels are of the “one-size-fits-all” variety, and are designed and built to accommodate the largest of such objects or prototypes. Because different objects may be expected to encounter flows of air or other gases at different velocities or pressures, a multipurpose wind tunnel must include fans, turbines, motors, machinery, or other pressure sources for generating flows of such gases at desired velocities or pressures. Likewise, the enclosures within which such machinery and the objects to be tested are provided must also be designed to accommodate and withstand not only the flows of gases at such velocities or pressures but also the physical impact of any particles or liquids that may be charged or injected into such flows for simulation purposes.
The rigorous structural and mechanical requirements that wind tunnels must satisfy necessarily increase their costs. Furthermore, when maintenance or repairs are performed on any aspect of a wind tunnel, the entire wind tunnel must be shut down and secured until such maintenance or repairs have been satisfactorily completed.